Presentation on theme: "Introduction to Atoms, Ions and Isotopes"— Presentation transcript:
1 Introduction to Atoms, Ions and Isotopes Chapter 5: Atomic Structure
2 What are atoms?The atom is a basic unit of matter that consists of a dense, central nucleus surrounded by a cloud of negatively charged electrons.While all atoms have protons, neutrons and electrons, atoms of different elements have different numbers of these.
3 AtomsEach element on the periodic table has an atomic number, which tells how many protons an atom of that element has.Each element also has an mass number.Mass number = # of Protons + # of NeutronsAmu = atomic mass unit
4 ElectronsNeutral atoms have the same number of electrons (negative charge) as they do protons (positive charge).# of electrons = atomic numberONLY IN NEUTRAL ATOMS
5 Let’s Practice! Find Boron on the periodic table. How many protons does an atom of Boron have?How many neutrons?Assume the mass number is 11How many electrons?
6 IsotopesAll neutral atoms of the same element have the same number of protons, and therefore the same number of electrons.The number of neutrons CAN vary.Isotopes: atoms of an element that have the same number of protons, but a different number of neutrons.
8 Average Atomic Mass vs. Mass Number The mass shown on your periodic table as a decimal is the average atomic mass of all isotopes of an atom in nature.By contrast, Mass Numbers are not on the periodic table – but must be given for each atom. The mass number is the sum of protons and neutrons in one atom of that element
9 Example: Lithium2 Isotopes are found in nature: Lithium-6 and Lithium-7 (Lithium-8 is radioactive and quickly decays)Atomic mass is listed as 6.94.How is that possible?94% of Li atoms have an atomic mass of 7, and 6% have an atomic mass of 6.Avg. Atomic Mass = (7 x .94) + (6 x .06)
10 IonsAn atom or small molecule with an overall positive or negative charge due to an imbalance of protons and electrons.# of protons does not change# of electrons changes.Positive charge = loss of electronsNegative charge = gain of electron
11 Ions Continued…Ions are represented by a superscript charge on the element symbol.Examples: F-, Mg2+, Al3+Practice:How many protons, neutrons, and electrons does Al3+ have?
12 Let’s Review! ________ are charged atoms. _________ ions have LOST electrons._________ ions have GAINED electrons.An atom of Cu2+ with mass number 63 has:________ protons________ neutrons________ electrons
13 More Review____________ are atoms of the same element that have different numbers of neutrons in the nucleus.What does average atomic mass represent?
14 Complete Atomic Structure Practice Problems Hint: Chromium-52 means Chromium with a mass number of Fe means iron with atomic number 26.